Electrical furnace and removable heating unit therefor



May 27",- 2924 1,495,503 1 P A. E. ARMSTRONG I ELECTRICAL FURNACE AND REMOVABLE HEATING UNIT THEREFOR M. 5 r .l. w m w i 5 m ANN! M 6 m B)- w M .S j v a -w 4 w 5 2 h m .a. M, Q E m 5 0 "m MW INVENTORY ATTORNEY May 27 1924. v

- I v P. A. E. ARMSTRONG I ELECTRICAL FURNACE AND REMOVABLE HEATING UNIT THEREFOR E'iled March 25 1920 I s Sheets-$heet 2 1 WEI-13R May 27 1924. 1,495,503

P. A. ARMSTRONG ELECTRICAL FURNACE AND REMOVABLE HEATING UNIT THEREFOR Filed March 25 1920- C Sheets-Sheet 5 A VIIIII/Il/Al/I/l/III/II/l INVENTOR a grown Patented M... 27, 1924.

UNITED STATES PATENT OFFICE.

ERGY A. E. ARMSTRONG, OF LOU DONVILLE, NEW YORK.

ELECTRICAL FURNACE AND REMOVABIJE HEATING UNIT THEREFOR.

Application filed Ital-ch 25, 1920. Serial No. 368,519.

To all whom it may concern.

- Be it known that I, PERCY A. E. Amsrs- STRONG, a subject of the King of Great Britian, and residing at Loudonville, in the 'county of Albany, State of New York, have invented certain new and useful Improvements in Electrical Furnaces and Removable Heating Units Therefor, of which the following is a specification.

My invention relates to electrical furnaces and removable heating units therefor.

One of the' i'objects of my invention is the provision of insulated electrical heating elements {or furnaces and the like which can be readily taken out and replaced or renewed, as occasion may arise therefor, thus enabling individual burnt out heating eleis heat resistant and is not readily frangible at the high temperatures emplo ed, with the heating elements extending t rough such perforations. When the heating elements are of hairin formationpwhich is the form common y used, the bricks of alundum,

or the like material, may each be provided with a pair of holesorpassages arranged substantially parallel to one another and through which the two branches ofthe heating element may extend, or separate bricks may be provided for each side member. Instead of using separate bricks, or sections of the insulating material, same may be cast or otherwise formed so as to extend for substantially the entire length of the heating element.

Other objects of my invention will appear in connection with the following description. 1

In the accompanying'drawings Fig. 1 is 'a view in perspective, with parts broken away, of; one formof furnace making. use

of my invention. Fig. 2 is across-sectional view of a circular furnace. Fig. 3 is a crosssectional view of an insulated heating unit. Fig. 4 is a part sectional view of a plurality ing readily broken.

of protected heating elements connected in series. Fig. 5 is an isometrical view showing two forms of insulating bricks. Fig. 6 is a cross-sectional view of a vertical fur nace. Figs. 7 and 8 are detail modifications of arts of the vertical furnace. Figs. 9, 10 an 11 are cross-sectional. views of modified forms of=insulated heating units, and Figs. 12 and 13 are cross-sectional views of circular furnaces of modified form.

I have illustrated heating elements 10 of the familiar hair-pin form. Blocks or bricks perforated for the passage of the heating element are provided, ofalundum, or other refractory insulating material, adapted to withstand high heat without be material for this purpose, but other materials having similar. properties may be used. The bricks may be of various forms. For example, the bricks may be of the fiatsided type, as shown at 11, or of interlocking type 11 with recesses 13 on one side and corresponding projections 1 1 on the op- .posite side, adapted to be nested in the recesses 13. The bricks may be of sufficient Alundum is a good.

length to have two parallel passages 15, 15' a formed therein and adapted to receive both side members 10 of the elements 10, or

single bricks 11 may be provided with single passages 15' for each of the side members 10', and such bricks 11 may be used on the connecting or base portion 10." of the heating element, if desired. Where the bricks with two holes are used, the base portion 10" of the heating elements may be received in recesses 16 of hollowed out bricks 17, if desired, such end bricks 17 being referably put into place after insertion in t e furnace of the removable heating units, comprising the heating element 10 withbrickssuch as 11, 11, 11", or insulating materialof other forms, in place thereon, and designated generally by reference character 18. I

The rotected or insulated units 18, made up of t e heating elements 10 in the form of wires, bars, rods, and the like, with the bricks striing thereon, or, in other words, consisting of a series of the bricks with the o enings therein aligned and the heating e ements passing through the passages thus provided, may be made use of in various ways and relations. For example, to give a s mple instance, one or more of such units nmy be laid on the ground or on a concrete "annealing of metallic articles, and such furnaces are lllustrated herein, but without limitation of the invention thereto. I

In Fig. 1 is shown a furnace of a form used for heat treatment of metallic products, such as tool steel and the like.

The inner shell or lining may he of'clay or other suitable heat resisting material. but

preferably is made of metallic material adapted to withstand high heat without substantial oxidation, corrosion and the like. For example, I preferably use stable surface alloy steel, as described in my Patent No.- 1,322,511, granted November 1919,

which is well adapted for this purpose.

The shell 20 is surrounded by a second shell 21, whicliniay be of similar material to shell 20, leaving an intermediate space 22 for the reception of the heating units 18 described above. The space outside the shell 21 and in rear of shell 20 is packed with suit.- able insulating material 22 and the whole ,enclosed in a suitable jacket 23.

Irovion is made for inserting and removing the heating units separately or singly. c.

The ends 10 of the side portions 10 of elements 10 may extend through openings '24 in the back plate 25, being insulated facilitated by making plate parts, if desired.

therefrom by insulating sleeves 26, and may be connected up electrically in any desired wvay, as by means of lugs 27 (Fig. 4), Series connection is illustrated for simplicity, but any desired arrangement may, of course, be used. Lugs 27 may be attached'by screws. .or othe wise, so as to be readily connected and disconnected.

In the form shown the units 18 are removed and replaced from the front end of the furnace,.the front plate 28 being made removable for this purpose.

l/Vhen replacement is to be made, as for example, of-a burnt out element, the plate 28 is removed, the corresponding lugs 27 disconnected, and the unit withdrawn and a new one inserted inits-place, and the parts replaced as before. hen other units are supported on the one desired to be replaced, it may be necessary when removing same to let the supported units move down one space and insert the new unit at the top. which can easily be done. The end brick 17 is preferably put in place last after .the unit is in place. Removal and replacement may be 28 in several The furnace doors should preferably be of such design that they can be readily removed to give access to plate In the form shown the doors 2%). 29 are sli'dably supported on guide rod 30 and kept in place by slide-way 31 and are opened by the op erator stepping on pedal '52, which is connected by link 33 to the counterweighted lever 34 from the opposite arms whereof links 35 and 36 run to the doors. lVhen the foot is removed from pedal 32. the doors are autonuitically closed by the. counterweight. Links 35 and 36 preferably have a pin and slot connection with the doors so that they may be readily disconnected.

The invention may be applied to. furnaces of various types as square, rectangular, elliptical, round, etc., etc. In Fig. 2 a cross section of a roundfurnace is shown, the inner shell 20 of which .is provided with ribs 20,

whereby it is spaced from the surrounding shell 21, and trays 37, 38 are provided for the reception of annealing boxes and the like. These trays are preferably of the same material as .the inner shell and it is to be noted that when annealing boxes and the like are pushed in,,moved around. and pulled out, it is of great advantage to have the furnace base or shelves of the alloy steel described qwhich is notgougeil or broken out thereby, as commonly happens with furnaces made of clay 01' the like materials.

-Heating units are removed and replaced in the circular furnaces in the manner already described, any units supported by the one removed,'being permitted to move down a space and the new element inserted at the top of the quadrant or other division.

In Fig. 9 I have illustrated a heating element provided with bricks 11 having one hole each for receiving the side member 10' of heating elements 10. The heating unit of Fig. 10 is similar to that of Fig. 9, but instead of bricks the insulating means is 7 formed in a single piece 11, for each side member of the heating element, which may be cast in place on the heating, element or separately formed, and the element inserted therein. In Fig. 11 I have shown a single insulating member 11, through which both side members of theiheating element extend,

Fig. 12 shows a modified form of furnace making use of heating units comprising bricks 11", as shown in'Fig. 9. In this form the shell 20 is provided with alternate. preferably integrally cast, ribs 40 and intermediate recesses 'vtl having the bottoms -12 thereof rounded or otherwise formed so that the insulating means such as bricksll ot' the heating units can fit closely therein. Removal and replacement of these units is ac complished-in the manner already described, but the replacement unit is always put back into the same place as the one taken'out.

The bricks 11 may be placed around the of Fig. 12, but ribs 40 of shell 20 thereof base portion 10 of the heating element 10, as shown in Figs. 9, 10 and 13, or, if desired, same may be dispensed with at the base of the heating element, so long as same does not come into contact with conducting surfaces.

The furnace of Fig. 13 is similar to that are shorter, and the shell 21 is spaced a proper distance from shell 20 by suitable spacing means, as indicated at 43.

The constructions shown in Figs. 12 and 13 enable the heating element to be placed substantially close to the inner wall of the shell lining, giving efficient heating results, but, nevertheless, the metallic lining material has 'sufiicient mass to hold heat for considerable periods and to secure gradual heating and cooling of the furnace which is desirable, for example, in annealing.

In Fig. 6 I have shown a vertical cylindrical furnace 45 such as used, for example, in gun shops.

The protected units 18 are arranged in banks 46, 46 about the interior of the furnace walls. They may be supported in various ways, as, for example, on projecting bricks 47, as shown-in Figs. 6 and 7, or by means of studs 48 of heat resisting material or metal set in the furnace'wall and received in loops 10 of the heating elements 10, with the insulating sleeve49 of alundum or the like material interposed therebetwee'n'.

' While I have shown certain forms of apparatus in which my invention may be embodied, it will be understood't-hat same are only for illustrating the invention and affording a clear understanding thereof and arenot to limit the invention.

I claim 1. A unitary electrical heating unit com-- prising a plurality of insulating, heat resisting bricks each having a pair of parallel aligned apertures, and an electrical heating element of hair-pin form extendin within the passages so formed, such unit being adapted to be separately inserted in or re- 4 moved from a heating device such as afur nace or the like. I 3

2. As a new article of manufacture, a unitary heating element for electricallieating comprising a plurality of heat resistant bricks each provided with a hole, and. astrong metallic electrical heating element extending through said holes, said heating element being complete in itself and adapted to be bodily inserted in or removed from a furnace or likelieating device.

3. An electric furnace having a chambered wall, and heating units comprising strong metallic electrical heating elements and in sulating members strung thereon, said units being removably and replaceably received within the chamber in the furnace wall.

4. An electric furnace having a chamber of heating units comprising heating elements and insulating members strung thereon and said units being adapted to be removed one by one through the opening in the front of said furnace provided by the removal of said closure. r 6. An electric furnace comprising an interior liping member and a chamber about said lining member extending lengthwise of the furnace a removable closure for said chamber at one end of said furnace and a plurality of heating units comprising'electrical heating elements and insulating means received within said chamber and said heating units being adapted to be WlthdlitWItOIlG by one from said chamber through the opening provided by removal of said closure.

7'. In an electric furnace, a lining shell, a heating element chamber extending substantially around said shell, a series of separate heating unitsadapted to be removably 'reresistant alloy-steel and a series of unitary electrical heating elements surrounding said lining and each adapted to be separately inserted or removed in the direction of its length.

9. In an electric furnace, a lining shell of heat resisting metallic material, a series of separate unitary heating units surrounding said lining and extending substantially parallel to the longitudinal axis thereof, said heating units comprising electrical heating elements and insulating members strung thereon, the upper heating units in the series being adapted to rest upon and be supported by those below.

10. In an electric furnace, a lining of heat resisting metallic material, a series of longitudinally removable unitary heating units arranged substantially to surround said lining, said heating units comprising heating elements and insulating members strung thereon, the heating elements lower down in the furnace serving to support those arranged thereabove, whereby when one of the lower-down heating units is removed, the

in the wall and a liningseparating the heating units above the same are moved downward and a replacement element may be inserted at the top of the series, I

11. In an electric'furnace, a lining of heat resistant metallic material, a series of longitudinally removable heating units arranged about the lining, said units comprising electrical 'heating elements of hair-pin form and insulating members strung there on. the base orconnecting portion of the hair-pin heating elements being directed toward the front of the furnace and a removable closure for the heating element spaces arranged at the front of the furnace and adapted, upon its removal, to permit the withdrawal from the forward end of the furnace of said heating elements in unitary form;

12. In an electric furnace, a lining of heatresisting metallic material, said lining being provided on its exterior with a series of grooves separated by intermediate ribs, and heating units, arranged about the lining and comprising electrical heating elements and insulatingmembers strung thereon and of a form adapted to be received and fitted in said grooves.

13. An electric furnace comprising a heatresisting metallic lining having a series of grooves formed in the exterior wall thereof and arranged substantially parallel to the longitudinal axis of the lining, said grooves being arranged in pairs with intermediate ribs therebetween, and aseries 'of heating units comprising electrical heating elements of hair-pin form and insulating members strung thereon and adapted to be received -Wltl'ill1 said grooves. and a removable closare at the end of said furnace adjacent to the base orqconnecting portion of said hairpin heating elements, whereby, upon removal of said. closure,- said heating. units or replacement.

1 In an electric furnace, a lining of heatresisting metallic material provided with grooves in its outer surface, and hair pin electrical heating elements, .the separated side portions thereof being provided with insulating members arranged thereon, said heating units being adapted to be arranged about said lining with the insulating members received within said grooves.

15. In an electric furnace, a lining shell of heat-resisting material, a shell'of similar material surrounding said lining and spaced therefrom to provide an'ii'i'termediate chammay be longitudinally withdrawn for repair ber, a plurality of heating units comprisingelectrical heating elements of hair-pin form, and perforated bricks of heat-resisting and insulating material strung thereon and having the separated ends, of the side portions of su clrhair-pin heating elements projecting separately from the furnace at one end for the attachment of electri :11 connections, and a removable closure for the chamber between said shells at the opposite end of said furnace, whereby said heating units may be removed and replaced by longitudi nal movement through the opening left by the removal of said closure.

In. witness whereof, I have signed my name hereto.

PERCY A. ARMSTRONG. 

